Author Topic: ESA - Gaia updates  (Read 56400 times)

Offline Star One

  • Senior Member
  • *****
  • Posts: 9643
  • UK
  • Liked: 1819
  • Likes Given: 183
Re: ESA - Gaia updates
« Reply #160 on: 05/03/2018 07:53 PM »
Evidence for Unresolved Exoplanet-hosting Binaries in Gaia DR2

Quote
This note describes an effort to detect additional stellar sources in known transiting exoplanet (TEP) systems, which are unresolved or barely resolved in the Gaia Data Release 2 (DR2) catalog (Gaia Collaboration et al. 2016, 2018). The presence of multiple unresolved stars in photometric and spectroscopic observations of a transiting planetary system biases measurements of the planet's radius, mass, and atmospheric conditions (e.g., Buchhave et al. 2011; Evans et al. 2016; Southworth & Evans 2016). In addition to the effect on individual planetary systems, the presence of unresolved stars across the sample of known exoplanets biases our overall understanding of planetary systems, due to the systematic underestimation of both masses and radii (Ciardi et al. 2015).

http://iopscience.iop.org/article/10.3847/2515-5172/aac173/meta

Offline Star One

  • Senior Member
  • *****
  • Posts: 9643
  • UK
  • Liked: 1819
  • Likes Given: 183
Re: ESA - Gaia updates
« Reply #161 on: 05/07/2018 07:45 PM »
Gaia Reveals Evidence for Merged White Dwarfs

We use Gaia Data Release 2 to identify 13,928 white dwarfs within 100 pc of the Sun. The exquisite astrometry and photometry from Gaia reveals for the first time a bifurcation in the observed white dwarf sequence in both Gaia and the Sloan Digital Sky Survey passbands. The latter is easily explained by a helium atmosphere (DB) white dwarf fraction of 36%. However, the bifurcation in the Gaia passbands cannot be explained by DB white dwarfs. We simulate theoretical color-magnitude diagrams for single and binary white dwarfs using a population synthesis approach and demonstrate that the only way to explain the bifurcation in the Gaia data is through a significant contribution from single white dwarfs that formed through mergers. This is the first direct detection of such a population in the solar neighborhood.

https://arxiv.org/abs/1805.01227

Offline AegeanBlue

  • Full Member
  • ****
  • Posts: 508
  • Raleigh
  • Liked: 127
  • Likes Given: 39
Re: ESA - Gaia updates
« Reply #162 on: 05/10/2018 09:09 PM »
Spain's contribution to Gaia DPAC:

https://www.res.es/en/news/gaia-creates-richest-star-map-our-galaxy-participation-two-res-nodes

There is also a large number of discoveries coming out of GaiaDR2. A twitter search for the hashtag #GaiaDR2 reveals quite a number of papers out. New stellar streams, new open star clusters, error margins in the DR2 parallaxes and other stuff. The typical method seems to be run a script on DR2, pull out interesting stars, cross check with other catalogs or at best a couple of days of observations and then publish your findings.

Offline philw1776

  • Full Member
  • ****
  • Posts: 1088
  • Seacoast NH
  • Liked: 728
  • Likes Given: 309
Re: ESA - Gaia updates
« Reply #163 on: 05/15/2018 04:45 PM »
Generic public article on early Gaia papers & results...
https://www.sciencenews.org/article/gaia-delivers-trove-data-revealing-secrets-milky-way

Couple of favorites interesting to me...

Improved radii for Kepler stars & exoplanets
https://arxiv.org/abs/1805.00231


Better Cepheid distances and problems with cosmic expansion rates
https://arxiv.org/abs/1804.10655

"Including the DR2 parallaxes with all prior distance ladder data raises the current tension between the late and early Universe route to the Hubble constant to 3.8 sigma (99.99 %)."
“When it looks more like an alien dreadnought, that’s when you know you’ve won.”

Offline Star One

  • Senior Member
  • *****
  • Posts: 9643
  • UK
  • Liked: 1819
  • Likes Given: 183
Re: ESA - Gaia updates
« Reply #164 on: 05/18/2018 03:42 PM »
ESA Euronews: Gaia’s revolution in astronomy


Offline AegeanBlue

  • Full Member
  • ****
  • Posts: 508
  • Raleigh
  • Liked: 127
  • Likes Given: 39
Re: ESA - Gaia updates
« Reply #165 on: 06/11/2018 06:55 PM »
The amount of research coming out of DR2 is just amazing. Last week there was a Gaia sprint in New York, and I found amazing just what they are trying to pull out of the data. The pitch slides are here:

https://docs.google.com/presentation/d/19_Un3VQrB9d7Ftczf9yNxoJkW6BDe-EtDbrjSR6mMHY/edit#slide=id.p

On Gaia news, as I read them on twitter, they are trying to pull out binaries misclassified as single stars out of the spectra based on their position on the H-R diagram. Also it seems that in DR2 galaxies were misclassified as variable stars because of the way Gaia scans: Galaxies are, for the most part, not spherical. Since Gaia sees the star in different angles, it passes a different cross section of the galaxy with a different brightness leading to the misclassification. As someone who measured classification error in land cover datasets for the first part of his dissertation, I feel empathy for the researchers.

Offline AegeanBlue

  • Full Member
  • ****
  • Posts: 508
  • Raleigh
  • Liked: 127
  • Likes Given: 39
Re: ESA - Gaia updates
« Reply #166 on: 06/23/2018 07:41 AM »
Another new Gaia discovery that popped up on twitter today: there is a gap in the HR main sequence stars. This seems to correspond to where dwarfs transition to partial to fully convective. The Gaia team members have weighed in on twitter and do not believe that this is a systematic error, rather a real effect.

arXiv paper: https://arxiv.org/abs/1806.07792

A Gap in the Lower Main Sequence Revealed by Gaia Data Release 2

Synopsis: We present the discovery of a gap near MG≈10 in the main sequence on the Hertzsprung-Russell Diagram (HRD) based on measurements presented in Gaia Data Release 2 (DR2). Using an observational form of the HRD with MG representing luminosity and GBP−GRP representing temperature, the gap presents a diagonal feature that dips toward lower luminosities at redder colors. The gap is seen in samples extracted from DR2 with various distances, and is not unique to the {\it Gaia} photometry --- it also appears when using near-IR photometry (J−Ks vs MKs). The gap is very narrow (∼0.05 mag) and is near the luminosity-temperature regime where M dwarf stars transition from partially to fully convective, i.e., near spectral type M3.0V. This gap provides a new feature in the H-R Diagram that hints at an underlying astrophysical cause and we propose that it is linked to the onset of full convection in M dwarfs.

Offline CuddlyRocket

Re: ESA - Gaia updates
« Reply #167 on: 06/24/2018 01:19 AM »
Another new Gaia discovery that popped up on twitter today: there is a gap in the HR main sequence stars.

So, who's this gap going to be named after? :)

Offline Ben the Space Brit

  • Senior Member
  • *****
  • Posts: 7140
  • A spaceflight fan
  • London, UK
  • Liked: 662
  • Likes Given: 771
Re: ESA - Gaia updates
« Reply #168 on: 06/24/2018 07:35 AM »
That's interesting. Might there be a 'threshold energy' required to jump into full convection that's lower than the linear energy increase just below M3?
"Oops! I left the silly thing in reverse!" - Duck Dodgers

~*~*~*~

The Space Shuttle Program - 1981-2011

The time for words has passed; The time has come to put up or shut up!
DON'T PROPAGANDISE, FLY!!!

Offline jebbo

  • Full Member
  • ****
  • Posts: 627
  • Cambridge, UK
  • Liked: 260
  • Likes Given: 241
Re: ESA - Gaia updates
« Reply #169 on: 06/25/2018 07:54 AM »
I think you have that the wrong way around: dwarfs *later* (smaller) than M3V are fully convective.

So it seems to imply an energy threshold for developing an outer radiative zone.

--- Tony

Offline AegeanBlue

  • Full Member
  • ****
  • Posts: 508
  • Raleigh
  • Liked: 127
  • Likes Given: 39
Re: ESA - Gaia updates
« Reply #170 on: 06/25/2018 09:36 PM »
Another new Gaia discovery that popped up on twitter today: there is a gap in the HR main sequence stars.

So, who's this gap going to be named after? :)

How about Van Ness gap? In downtown Fresno, the next street over from Fulton Street is Van Ness Street. And sure, Fulton is a person and Fresno is pretty obscure as a place, but that doesn't mean we should have fun :)

On a more serious note there was a Gaia workshop in Heidelberg last week, not to be confused with the one in Barcelona taking place this week, and the presentations are up at:
http://gaia.ari.uni-heidelberg.de/gaia-workshop-2018/programme.html

Most interestingly in the very first presentation by Biermann there is the last slide (attached)



Offline AegeanBlue

  • Full Member
  • ****
  • Posts: 508
  • Raleigh
  • Liked: 127
  • Likes Given: 39
Re: ESA - Gaia updates
« Reply #171 on: 07/03/2018 07:10 AM »
Speaking of gaps, this paper, based on Gaia and Kepler claims that there are gaps at 2 Earth radii (rocky planets), 4 Earth radii (water worlds) and 10 Earth radii (transition worlds to gas giants above 10)

https://arxiv.org/abs/1806.11234

Abstract:
<quote> Applying the survival function analysis to the planet radius distribution of the Kepler confirmed/candidate planets, we have identified two natural divisions of planet radius at 4 Earth radii and 10 Earth radii. These divisions place constraints on planet formation and interior structure model. The division at 4 Earth radii separates small exoplanets from large exoplanets above. When combined with the recently-discovered radius gap at 2 Earth radii, it supports the treatment of planets 2-4 Earth radii as a separate group, likely water worlds. For planets around solar-type FGK main-sequence stars, we argue that 2 Earth radii is the separation between water-poor and water-rich planets, and 4 Earth radii is the separation between gas-poor and gas-rich planets. We confirm that the slope of survival function in between 4 and 10 Earth radii to be shallower compared to either ends, indicating a relative paucity of planets in between 4-10 Earth radii, namely, the sub-Saturnian desert there. We name them transitional planets, as they form a bridge between the gas-poor small planets and gas giants. Accordingly, we propose the following classification scheme: (<2 Earth radii) rocky planets, (2-4 Earth radii) water worlds, (4-10 Earth radii) transitional planets, and (>10 Earth radii) gas giants.  </quote>

Offline AegeanBlue

  • Full Member
  • ****
  • Posts: 508
  • Raleigh
  • Liked: 127
  • Likes Given: 39
Re: ESA - Gaia updates
« Reply #172 on: 07/05/2018 07:40 AM »
Discovery of the day: the Milky Way collided early in its history with a galaxy dubbed "the Gaia Sausage" and this is visible in radial velocities:

https://www.simonsfoundation.org/2018/07/04/gaia-sausage-galaxy/

Now usually when scientists want to say something more elegantly than their mother tongue and obfuscate a colloquialism, they use ancient Greek. Ancient Greek for sausage is "άλλας", or allas to spell it in the Latin alphabet. Could it be that in the future this progenitor galaxy will be known as the Allas Galaxy rather than the Gaia sausage?

Offline AegeanBlue

  • Full Member
  • ****
  • Posts: 508
  • Raleigh
  • Liked: 127
  • Likes Given: 39
Re: ESA - Gaia updates
« Reply #173 on: 08/18/2018 07:16 AM »
Gaia is the give that keeps on giving, as it has been called, and is the star in a series of astronomy conferences. Many of those conferences I did not know that they existed, but then again I am not an astronomer. Now CoolStars20 has put up both slides and lectures up, and from that here is a Gaia mission overview:

https://coolstars20.github.io/talkpdf/Thevenin.pdf

Offline bolun

  • Senior Member
  • *****
  • Posts: 2801
  • Europe
  • Liked: 233
  • Likes Given: 70
Re: ESA - Gaia updates
« Reply #174 on: 08/21/2018 03:50 PM »

Offline AegeanBlue

  • Full Member
  • ****
  • Posts: 508
  • Raleigh
  • Liked: 127
  • Likes Given: 39
Re: ESA - Gaia updates
« Reply #175 on: 09/13/2018 08:47 PM »
Impressions from the IAU general assembly

https://www.cosmos.esa.int/web/gaia/iow_20180911

Gaia had an entire session dedicated to it, and on the ESA booth they had demonstrations on how to use its data and a VR exhibit using GaiaSky that allowed to experience the Gaia mapped part of the galaxy in 3-D, or so I read. The news release contains links to the slides from 5 presentations. Gaia DR3 is now expected early 2021 rather than late 2020 previously. They are characterizing errors and biases better, setting up new pipelines for new products (such as the 100,000+ solar system objects) and tweaking their code. From what I read, if it was just an issue of doing DR2 with more data, DR3 would have been released already

Offline bolun

  • Senior Member
  • *****
  • Posts: 2801
  • Europe
  • Liked: 233
  • Likes Given: 70
Re: ESA - Gaia updates
« Reply #176 on: 09/20/2018 12:53 PM »
Gaia hints at our Galaxy's turbulent life

19 September 2018

ESA's star mapping mission, Gaia, has shown our Milky Way galaxy is still enduring the effects of a near collision that set millions of stars moving like ripples on a pond.

The close encounter likely took place sometime in the past 300–900 million years. It was discovered because of the pattern of movement it has given to stars in the Milky Way disc – one of the major components of our Galaxy.

The pattern was revealed because Gaia not only accurately measures the positions of more than a billion stars but also precisely measures their velocities on the plane of the sky. For a subset of a few million stars, Gaia provided an estimate of the full three-dimensional velocities, allowing a study of stellar motion using the combination of position and velocity, which is known as 'phase space'.

In phase space, the stellar motions revealed an interesting and totally unexpected pattern when the star's positions were plotted against their velocities. Teresa Antoja from Universitat de Barcelona, Spain, who led the research couldn't quite believe her eyes when she first saw it on her computer screen.

One shape in particular caught her attention. It was a snail shell-like pattern in the graph that plotted the stars' altitude above or below the plane of the Galaxy against their velocity in the same direction. It had never been seen before.

http://sci.esa.int/gaia/60663-gaia-hints-at-our-galaxys-turbulent-life/

Image credit: ESA, CC BY-SA 3.0 IGO

Offline bolun

  • Senior Member
  • *****
  • Posts: 2801
  • Europe
  • Liked: 233
  • Likes Given: 70
Re: ESA - Gaia updates
« Reply #177 on: 09/25/2018 06:42 PM »
http://www.esa.int/Our_Activities/Space_Science/Gaia/Gaia_finds_candidates_for_interstellar_Oumuamua_s_home

Gaia finds candidates for interstellar 'Oumuamua's home

Quote
Using data from ESA’s Gaia stellar surveyor, astronomers have identified four stars that are possible places of origin of ‘Oumuamua, an interstellar object spotted during a brief visit to our Solar System in 2017.

Quote
While future observations of these four stars might shed new light on their properties and potential to be the home system of ‘Oumuamua, the astronomers are also looking forward to future releases of Gaia data. At least two are planned in the 2020s, which will include a much larger sample of radial velocities, enabling them to reconstruct and investigate the trajectories of many more stars.



Offline bolun

  • Senior Member
  • *****
  • Posts: 2801
  • Europe
  • Liked: 233
  • Likes Given: 70
Re: ESA - Gaia updates
« Reply #178 on: 10/02/2018 03:22 PM »

Offline AegeanBlue

  • Full Member
  • ****
  • Posts: 508
  • Raleigh
  • Liked: 127
  • Likes Given: 39
Re: ESA - Gaia updates
« Reply #179 on: 10/06/2018 06:50 AM »
Gaia - The stereoscopic survey of the galaxy



This is a lecture at the colloquium of the Harvard - Smithsonian Center for Astrophysics. It is thus at a higher level than press events intended for the general public but not as complicated as a conference lecture. This is not a lecture about what they found in the catalog. It is a lecture on the mission from its inception in 1993 to today. It is very interesting when talking about all the science that Gaia is doing that its very high accuracy allows: For example they are detecting the relativistic bending of light by Jupiter at the 2000σ level, and in 2019 in honor of the century since Eddington measured the bending of the stars during an eclipse as Einstein predicted they intend to measure the effects from the rotation of Jupiter. I really liked this lecture.

Tags: gaia