Image: Star π1 Gruis

Astronomers using ESO’s Very Large Telescope have directly observed granulation patterns on the surface of a star outside the Solar System — the ageing red giant π1 Gruis. This remarkable new image from the PIONIER instrument reveals the convective cells that make up the surface of this huge star. Each cell covers more than a quarter of the star’s diameter and measures about 120 million kilometers across. Image Credit: ESO


 
Astronomers using ESO’s Very Large Telescope have for the first time directly observed granulation patterns on the surface of a star outside the Solar System — the ageing red giant π1 Gruis. This remarkable new image from the PIONIER instrument reveals the convective cells that make up the surface of this huge star, which has 700 times the diameter of the Sun. Each cell covers more than a quarter of the star’s diameter and measures about 120 million kilometers across. These new results are being published this week in the journal Nature.

Located 530 light-years from Earth in the constellation of Grus (The Crane), π1 Gruis is a cool red giant. It has about the same mass as our Sun, but is 700 times larger and several thousand times as bright. Our Sun will swell to become a similar red giant star in about five billion years.

An international team of astronomers led by Claudia Paladini (ESO) used the PIONIER instrument on European Southern Observatory’s (ESO’s) Very Large Telescope to observe π1 Gruis in greater detail than ever before. They found that the surface of this red giant has just a few convective cells, or granules, that are each about 120 million kilometers across — about a quarter of the star’s diameter. Just one of these granules would extend from the Sun to beyond Venus. The surfaces — known as photospheres — of many giant stars are obscured by dust, which hinders observations. However, in the case of π1 Gruis, although dust is present far from the star, it does not have a significant effect on the new infrared observations.

When π1 Gruis ran out of hydrogen to burn long ago, this ancient star ceased the first stage of its nuclear fusion program. It shrank as it ran out of energy, causing it to heat up to over 100 million degrees. These extreme temperatures fueled the star’s next phase as it began to fuse helium into heavier atoms such as carbon and oxygen. This intensely hot core then expelled the star’s outer layers, causing it to balloon to hundreds of times larger than its original size. The star we see today is a variable red giant. Until now, the surface of one of these stars has never before been imaged in detail.

By comparison, the Sun’s photosphere contains about two million convective cells, with typical diameters of just 1,500 kilometers. The vast size differences in the convective cells of these two stars can be explained in part by their varying surface gravities. π1 Gruis is just 1.5 times the mass of our Sun but much larger, resulting in a much lower surface gravity and just a few, extremely large, granules.

While stars more massive than eight solar masses end their lives in dramatic supernovae explosions, less massive stars like this one gradually expel their outer layers, resulting in beautiful planetary nebulae. Previous studies of π1 Gruis found a shell of material 0.9 light-years away from the central star, thought to have been ejected around 20,000 years ago. This relatively short period in a star’s life lasts just a few tens of thousands of years – compared to the overall lifetime of several billion – and these observations reveal a new method for probing this fleeting red giant phase.

Photo: "Solstice Skies over Stephens" Photo by David Dreimiller.

“Solstice Skies over Stephens” Photo by David Dreimiller. While it’s not actually solstice quite yet, the low sun and cloudy skies certainly go with the season!

 

The date of our final scheduled observatory Open Night has passed and Stephens Memorial Observatory will close for the season. If we enjoy a stretch of clear nights this winter, we may open for a special Open Night event (we would love to show you the Orion Nebula) so watch this website and our Twitter feed for updates. Otherwise, we’ll hope to reopen in March for monthly sessions. Until then, we wish you a happy holiday season and a new year full of peace and happiness.

Open Night Canceled

StephensAstro —  December 15, 2017 — Leave a comment

Due to current and predicted weather conditions, tonight’s scheduled Open Night at the Observatory has been CANCELED. If driving conditions are safe, please consider attending a free, fun indoor StarLab planetarium presentation tonight. See the previous post for all of the details….

Photo: StarLab Portable Planetarium

StarLab Portable Planetarium


 
We expect we will cancel our scheduled Friday night Observatory event due to cloudy skies and possible snow. There is, however, a special treat awaiting sky-watchers on campus and it’s indoors, you know, where it’s warm!

The portable StarLab planetarium will be set up and open to the public! Free of charge! No tickets required! Folks can just come any time from 7:00 to 9:00 PM. The more the merrier. We will run 20-minute programs in the dome and have a few things planned while people are waiting or as they leave.

The StarLab will be set up in the Gerstacker science building on the Hiram College campus, not far north of the Post Office: 11700 Dean St.; Hiram.

So, come on out and enjoy a fun and informative evening snug inside StarLab. And to everyone we wish a happy holiday season, as well as peace and happiness in the coming new year!

Photo: The Pleiades

The Pleiades (M45) – By Rawastrodata

UPDATE: Due to inclement winter weather conditions, we expect we will CANCEL this planned event. Skies are predicted to be cloudy with a high likelihood of snow, and temperatures in the 20s can be expected.

Stephens Memorial Observatory of Hiram College will be open for public observing Friday, December 15, from 7:00 to 9:00 PM. Given good skies, visitors will see the stars of the Pleiades and Hyades clusters. Other objects of interest will also be sought. Most of the Observatory’s Open Nights take place on Saturdays but this special Friday event is in support of a related program on the Hiram campus.

Cloudy skies at the scheduled starting time cancel the event and in that case, the observatory will not open. No reservations are required and there is no admission fee for observatory public nights.

The Observatory is located on Wakefield Road (Rt. 82) less than a quarter of a mile west of Route 700 in Hiram. There is no parking at the Observatory. Visitors may park on permissible side streets near the Post Office, a short distance east of the observatory.

5:30 PM – UPDATE: Due to current and expected poor sky conditions, this scheduled Open Night has been CANCELED. We hope to have better luck on a special night: Friday, December 15.

Stephens Memorial Observatory of Hiram College will be open for public observing Saturday, November 25, from 7:00 to 9:00 PM. Given good skies, visitors will see the stars of the Pleiades and Hyades clusters. Other objects of interest will also be viewed. Early arrivals might get a look at the Moon but neighboring trees will either block us entirely or cut viewing short!

Cloudy skies at the scheduled starting time cancel the event and in that case, the observatory will not open. No reservations are required and there is no admission fee for observatory public nights.

The Observatory is located on Wakefield Road (Rt. 82) less than a quarter of a mile west of Route 700 in Hiram. There is no parking at the Observatory. Visitors may park on permissible side streets near the Post Office, a short distance east of the observatory.

Photo: Fireball Meteor, Oct. 20, 2017. Credit: NASA/All-Sky Fireball Network

A Grand Orionid Fireball Meteor Imaged over Hiram Friday, October 20. Credit: NASA/All-Sky Fireball Network

Earth is entering a stream of debris from Halley’s Comet, source of the annual Orionid meteor shower. Thursday night, NASA’s network of all-sky meteor cameras detected 23 Orionid fireballs over the USA –meteors that flare brighter than the planet Venus shines– a result of comet dust hitting the atmosphere at speeds exceeding 65 km/s (145,000 mph). Among several fireballs recorded by the Fireball Network camera on the Hiram campus was the grand meteoric streak pictured above; that fireball was also recorded by the camera located at the Allegheny Observatory in Pittsburgh in the wee hours of Friday morning. Forecasters expect the shower to peak on Oct. 21-22 with as many as 25 meteors per hour. The meteor shower is called “Orionid” because the “falling stars” appear to originate from the vicinity of our sky occupied constellation Orion. Visit Spaceweather.com for observing tips and sky maps. — From a report by Spaceweather.com plus local contribution.

Weather conditions may be best for us overnight Friday as the Orionids shower builds towards its peak. https://www.accuweather.com/

Weather conditions may be best for us overnight Friday as the Orionids shower builds towards its peak. https://www.accuweather.com/