Scheat (Beta Pegasi)

Scheat (Beta Pegasi) is a star in the constellation Pegasus, magnitude 2.4.

The Great Square’s red corner — a cool, swollen giant that slowly pulses.

Of the four stars of the Great Square of Pegasus, Scheat is the odd one out: a red giant among blue-white stars. Its name may come from the Arabic al-sāʿid, “the upper arm”, or from saʿd, and the same name was once given to Delta Aquarii, now called Skat.

Scheat has swollen to about 109 times the Sun’s width and shines 1,640 times as brightly, yet its surface is only about 3,600 kelvin — cool enough for molecules of titanium oxide to form in its atmosphere. In the Sun’s place, it would reach beyond the orbit of Mercury.

In 1847 Johann Friedrich Julius Schmidt discovered that it varies. Scheat is a semiregular variable star that brightens and fades over about 43 days, and it is slowly shedding gas and dust into an expanding shell.

Scheat (Beta Pegasi) is 200 light-years away: the light we see from it set off around 1825, 20 years before Neptune was discovered.

Did you know?

• A shell beyond Saturn. The gas and dust Scheat sheds form a shell that, around the Sun, would reach well beyond the orbit of Saturn.
• The Encampment. In Chinese astronomy Scheat and Markab form the Encampment, and Scheat is its second star, Shì Xiù èr.

An orange-red 2nd-magnitude star at the north-west corner of the Great Square of Pegasus. Its colour stands out against the Square’s white corners, and comparing it with Markab over a few weeks shows it brighten and fade.

What is a star?

When and where to see it

It is best placed in the evening sky around October, when it crosses the meridian at about 10 pm local time (around midnight in September). It can be seen from everywhere north of 62°S and never sets north of 62°N.

At its highest it stands 68° up from 50°N, 83° up from 35°N, 62° up from the equator, 27° up from 35°S.

Facts

Type

Star

Constellation

Pegasus

Designations

Beta Pegasi, β Peg, 53 Peg, HR 8775, HD 217906, HIP 113881

Magnitude

2.4

Position

RA 23h 3.8m, Dec +28° 5′ (J2000)

Spectral type

M2.5II-III

Colour

orange-red (B−V 1.67)

Distance

200 light-years

Discovered

Known since antiquity

Open AstroPilot to see when Scheat (Beta Pegasi) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.