What does Gaia see?
What does Gaia see? How does a star appear to move when observed from Earth?
There are three separate movements, one caused by Gaia – and us – moving with the Earth around the Sun, one caused by the stars moving through the Milky Way, and often a third wobble, caused by planets around the star. Let us look at each of these.
The first motion is an apparent motion, not real motion by the star. This motion, called parallax, is caused by our movement around the Sun.
But… what is a parallax?
Just hold a finger out in front of your face, close one eye at a time, and watch your finger appear to move compared to more distant objects. Parallax is how we see in 3-dimensions, and so know how far away things are from us on earth. In astronomy the effect is the same – but stars are at very large distances indeed. So we need to look from directions when the Earth has moved as far apart as possible – say summer and winter. We also need to measure very small apparent motions of the star.
A movie showing how Gaia measures stellar parallaxes can be found here!
The second motion of a star which Gaia will measure is real motion – it is the motion of each star in the Milky Way. The Sun moves around the centre of the Milky Way at a speed of about 220km/second (10,000,000,000 miles/hour), and most other stars move at similar speeds. The motion of this speed, called “proper” motion, will be measured by Gaia, and used to calculate how the star is orbiting in the Milky Way, and in some cases, where that star came from.
The third motion is caused by planets around a star. Many people imagine the Sun fixed at the centre of the Solar System, with the Earth and other planets orbiting around. This is not correct: as Newton first realised, the planets and Sun all orbit around the place which is the centre of all the mass in the system, including the planets. This centre moves as the planets move. Since Jupiter is quite heavy, this mass centre in the Solar System is just beyond the surface of the Sun – thus the Sun orbits, with a period of the Jupiter year, about this point. That is, stars wobble if they have heavy planets nearby. Gaia will measure this wobble, and so discover the planets.
The combination of all those motions, apparent and real, ensure each star moves in a very complex pattern across the sky. Untangling this complexity is why Gaia needs to make so many measurements – 80 on average – of every star.
Text source: Gaia in the UK
Picture on the banner: ESA/Gaia-CC BY-SA 3.0 IGO
RT @TechnologicDesk: #GaiaMission in the news! https://t.co/86OzGlMsJK Thanks to @idariane #gaiamission
RT @rdrimmel: #GaiaMission Announcement: "The science of Gaia and future challenges", Lund, Aug 30 - Sept 1 Registration NOW OPEN https://…
RT @StefanJordanARI: I enjoyed the talk at the ESAC data Workshop a lot! @cosmos4u @Jos_de_Bruijne #GaiaMission #GaiaDR1 https://t.co/k6ZV2…
RT @ESAGaia: Most #IAUS330 presentations + winning posters for Astrometry and Astrophysics in the #GaiaMission sky available now: https://t…
RT @yshalf: Spanish publication on #GaiaMission by our @GaiaUB colleagues: https://t.co/tDdLSEXJnW
Save the date! https://t.co/LAjhPQBjG0
RT @SpacemanSimon: I’ll be presenting the latest on #GaiaMission Photometric Alerts at EWASS this year. https://t.co/zH52QU0k1R
RT @ziggypao: Anthony Brown resuming the bright perspectives of #GaiaMission for the next data release, at the 'object processing' (cu4) me…
RT @rdrimmel: The latest #GaiaMission paper I shared was about calibrating variable stars. It's of cosmological importance: https://t.co/c0…
RT @StefanJordanARI: At #IAUS330 astronomers are presenting first results from the first #GaiaMission catalogue. A video on #GaiaDR1: http…
RT @StefanJordanARI: Fly through the stars of #GaiaMission ’s first star catalogue? Download Gaia Sky: https://t.co/kP6oaEsoiB https://t.co…
RT @TechnologicDesk: #GaiaMission in the news! https://t.co/szfFVavzj4 Thanks to @Jos_de_Bruijne @StefanJordanARI #gaiadr1 #supernova
RT @DMontesG: James Binney: Standard Galaxy - Selection Funtion ... #Gaiamission at the Gaia Sky #IAUS330gaia #IAUS330 https://t.co/oNX0aSq…
RT @DMontesG: David Hobbs: GaiaNIR #Gaiamission at the Gaia Sky #IAUS330gaia #IAUS330 https://t.co/Bi2rkflHNs
RT @rdrimmel: MT @FringeDoctor: Hobbs: parallax horizon with extended #GaiaMission plus GaiaNIR reaches to Galactic centre https://t.co/szE…
RT @DMontesG: Ivan Minchev @iminchev1: @APOGEEsurvey & @GalacticRAVE + 4MOST #Gaiamission at the Gaia Sky #IAUS330gaia #IAUS330 https://t.…
RT @DMontesG: Amina Helmi: nearby halo #Gaiamission at the Gaia Sky #IAUS330gaia #IAUS330 https://t.co/1XEQ9LzgRg
RT @DMontesG: Georges Kordopatis: MDF & @GalacticRAVE DR5 & #Gaiamission at the Gaia Sky #IAUS330gaia #IAUS330 https://t.co/Cs99PjOnh6
RT @StefanJordanARI: I just gave a talk on the #GaiaMission at a Gaia Workshop for 22 teachers parallel to the #IAUS330. It was fun and I g…
RT @DMontesG: Kohei Hattori: RAVE-TGAS Fe/H dependence Hercules MG #Gaiamission at the Gaia Sky #IAUS330gaia #IAUS330 https://t.co/RBSJPIOb…
Gaia-GOSA, an interactive tool for ground-based observations
Gaia-Groundbased Observation Service for Asteroids (Gaia-GOSA), a tool that let users behave as team members of the Gaia mission.
The Montsec Observatory and the Gaia science alerts
Welcome to the blog of the Gaiaverse portal!