# Yed Prior (Delta Ophiuchi)

Yed Prior (Delta Ophiuchi) is a star in the constellation Ophiuchus, magnitude 2.8.

**The Serpent-bearer’s hand — a red giant paired with a star that is no relation.**

Two stars hold the serpent’s head. Yed Prior and Yed Posterior mark the left hand of Ophiuchus, gripping the snake Serpens — yed comes from the Arabic yad, “hand”. Yed Prior gets its name because it leads its partner across the sky. Yet the two are neighbours only by chance: Yed Posterior is much closer to us.

Yed Prior is a [red](https://astropilot.space/glossary/star-colour) giant late in life, on what astronomers call the asymptotic giant branch. It has swollen to about 54 times the Sun’s width with only 1.5 times its mass, so its outer layers are far less dense than the Sun. Its surface glows at a cool 3,733 K, and it holds more than twice the Sun’s share of heavy elements.

Its light hints at something lopsided. It is strongly polarised, more so in blue light than red, and the effect changes over time — perhaps from an uneven shell of dust thrown off by the star, or from hot spots on its surface.

Yed Prior (Delta Ophiuchi) is 170 light-years away: the light we see from it set off around 1855, 10 years after Neptune was discovered.

## Did you know?

- **The state of Liang.** In Chinese astronomy Yed Prior is the ninth star of the Right Wall of the Heavenly Market Enclosure, where it represents the ancient state of Liang.
- **The Southern Line.** With Unukalhai and Zeta Ophiuchi it belonged to al-Nasaq al-Yamānī, “the Southern Line”, an Arabic star group of seven stars.

An orange-red star of magnitude 2.7, paired to the naked eye with Yed Posterior just over a degree to its south-east. Together they form the Serpent-bearer’s hand; compare the two and you will see that Yed Prior is the redder.

## When and where to see it

It is best placed in the evening sky around June, when it crosses the meridian at about 10 pm local time (around midnight in May). It can be seen from everywhere south of 86°N and never sets south of 86°S.

At its highest it stands 36° up from 50°N, 51° up from 35°N, 86° up from the equator, 59° up from 35°S.

## Facts

- Type: Star
- Constellation: Ophiuchus
- Designations: Delta Ophiuchi, δ Oph, 1 Oph, HR 6056, HD 146051, HIP 79593
- Magnitude: 2.8
- Position: RA 16h 14.3m, Dec −3° 42′ (J2000)
- Spectral type: M0.5III
- Colour: orange-red (B−V 1.59)
- Distance: 170 light-years
- Discovered: Known since antiquity

Open AstroPilot to see when Yed Prior (Delta Ophiuchi) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view. https://astropilot.space/object/yed-prior