Menu

Alkaid — Star in Ursa Major

HIP 67301; Eta Ursae Majoris; 85 Ursae Majoris

Magnitude 1.9m Star Ursa Major (UMa) Visible
Star Map
+ List + Plan

About Alkaid

Description

Alkaid (also known as Benetnash) is a blue main-sequence star of spectral type B3V, located about 101 light-years from Earth. At magnitude 1.86, it is the third brightest star in Ursa Major and marks the tip of the Big Dipper's handle (or the tail of the Great Bear). With a luminosity about 594 times that of the Sun and a surface temperature of roughly 15,500 K, it is one of the hottest stars easily visible to the naked eye.

Observing Tips

The end star of the Big Dipper's handle, Alkaid is easy to find from the northern hemisphere. It appears as a bright blue-white star. Follow the arc of the Dipper's handle past Alkaid to 'arc to Arcturus' — a famous navigation trick. Visible year-round from mid-northern latitudes, but best placed in the evening sky from March through August when the Big Dipper rides high overhead.

History

The name Alkaid derives from the Arabic 'al-qa'id,' meaning 'the leader' — specifically the leader of the mourners following a celestial funeral bier (the bowl of the Dipper being the bier). The alternate name Benetnash comes from Arabic 'banat na'sh,' meaning 'daughters of the bier.' Unlike the five inner stars of the Big Dipper, Alkaid is not a member of the Ursa Major Moving Group and will eventually cause the Dipper's shape to distort over thousands of years.

Fun Facts

Alkaid is the hottest and most luminous star in the Big Dipper. Because it is not part of the Ursa Major Moving Group that includes most of the other Dipper stars, it is moving in a different direction through space — in about 50,000 years, the familiar Dipper shape will be noticeably deformed.

Observe

1Physical Properties

Magnitude 1.86
Spectral Type B4V
Star Color Blue (B-V -0.19)
Distance 104 ly

2Position & Identifiers

RA 13h 47m 32.4s
Dec +49° 18' 48.0"
Constellation Ursa Major (UMa)
HR 5191
HIP 67301
HD 120315
SAO 44752
Bayer Eta
Flamsteed 85 UMa

3How easy to spot?

Sign in and configure your equipment and default location to see a personalized row.
Equipment Bortle 3 Bortle 4 Bortle 5
Naked eye Easy Easy Easy
50mm finder Easy Easy Easy
150mm scope Easy Easy Easy
Easy Medium Hard Very hard Impossible

Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs

4Visibility

Set a location in User Settings to see visibility data.

Best season Mar – May (peak: Apr)

5Survey Image

Loading survey image…

Explore

7

Size Comparison

Querying VizieR for stellar data…
8

Compare Stars

9

Spectral Classification

10

Hertzsprung-Russell Diagram

Loading HR diagram…
11

Stellar Lifecycle

12

Blackbody Spectrum

13

Stellar Absorption Spectrum

Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.

14

Stellar Fusion

Discover

15Stellar Notes

Color excess E(B-V) = +0.02.
Cas-Tau OB1; member of Pleiades group.
Lyman alpha observed from COPERNICUS.
ALKAID; Benetnash; Benetnasch; Elkeid.
16

Light Travel Time Machine

17

Relativistic Travel

}